Encapsulation machine with valved injection wedge

ABSTRACT

This invention relates to a method and apparatus for forming soft capsules and provides novel processing flexibility. The apparatus comprises a three-way valve injector wedge. This injector wedge allows for set-up of the encapsulation machine with a placebo fill and quick change over to active fill. This conserves use of the active ingredient.

TECHNICAL FIELD

[0001] This invention relates to an improved apparatus and method forproducing ingestible encapsulated products, such as soft capsules filledwith a liquid, suspension, solids, semi-solids, powders, tablets,medicines, nutrients and other materials. More specifically, theinvention is directed to the use of melt-on-demand devices and extrusiondies to produce a ribbon of encapsulating film. The improved apparatusmay also comprise a novel injection wedge.

BACKGROUND OF THE INVENTION

[0002] U.S. Pat. No. 1,970,396 to R. P. Scherer describes an earlymethod and machine for producing soft gelatin capsules in an automatedprocess. The process involves the formation of two gelatin sheets orfilms through the use of a gravity fed spreader box, cooling the liquidgelatin on two separate webs, then lubricating and guiding the twosheets into communication with each other between two co-acting dieswhile simultaneously dispensing the proper amount of medicine or otherfilling material between the sheets in registration with half cavitiesin the outer surface of the dies.

[0003] U.S. Pat. No. 4,817,367 to Ishikawa et al. introduced someimprovements to the basic machine to aid in the set up, operation andquality of the capsules produced, however, a gravity fed spreader boxwas still used to form the gelatin ribbons or sheets.

[0004] U.S. Pat. No. 5,761,886 to Parkhideh discloses an apparatus forforming capsules that provides rotary dies that are independentlymoveable and the ability to vary the speed of the dies during theformation of a single capsule. The Parkhideh device also utilizesindependently controlled casting drums to reduce “set-up” time andprovide better quality control. Even though Parkhideh discloses a verysophisticated encapsulation machine, it still utilizes a gravity feedspreader box for formation of the encapsulating ribbon. Other patentsrelating to encapsulation techniques which disclose the use of spreaderboxes to create the film or ribbon on a casting drum include U.S. Pat.No. 5,246,638 to Ratko et al.; U.S. Pat. No. 5,735,105 to Stroud et al.;U.S. Pat. No. 2,774,988 to Stirn et al.; U.S. Pat. No. 6,022,499 toSchurig et al.; and U.S. Pat. No. 2,288,327 to Scherer.

[0005] One interesting reference is U.S. Pat. No. 4,028,024 to Moreland.It discloses a process and apparatus that prepares a gelatin encasedmedicament. The gelatin and the active are co-extruded as a column. Thiscolumn is then pinched off by a pair of rotating wheels, each havinghalf cavities therein to form capsules.

[0006] These previously utilized machines have many structural andoperational shortcomings. Many of the shortcomings relate to the“set-up” of the machine. For example, the die to die timing, pumptiming, ribbon formation and wedge adjustments are all important inprotecting the equipment and providing a quality product. One aspect ofthe present invention resides in the use of a melt-on-demand extrusiontechnology and/or a valved wedge to decrease set-up time, reduce costsand improve product quality. The apparatus and process of the presentinvention allows for the use of encapsulating materials that werepreviously unusable on a standard rotary die encapsulation machine dueto high viscosities or processing temperatures.

[0007] A general discussion of the basic technology, apparatuses andprocesses relating to the preparation of soft capsules is described inThe Theory and Practice of Industrial Pharmacy (Lachman, Liberman andKanig) 3^(rd) edition, published by Lee & Febiger.

[0008] Conventional technology for the manufacture of soft capsulesusing the rotary die process typically utilizes a spreader box meteringsystem to cast the films or sheets onto a chilled surface, i.e., thecasting drum. The present invention differs from conventional technologyby the method of producing the sheets, ribbons or films. In theinventive process, extrusion dies are used as an alternative to spreaderboxes. Further, the film-forming composition is not kept molten butrather is allowed to solidify and only the amount needed is melted justprior to its placement on the casting drum. In addition, the novelvalved wedge according to the invention provides economical set-up ofthe encapsulation machine.

[0009] The conventional process of producing gelatin films comprisesmixing gelatin, plasticizers and water, and heating the mixture whilestirring under vacuum. The gelatin and excipients are heated undervacuum with mixing until a molten homogenous mixture is produced that isreferred to as a gelatin melt. This occurs at approximately 45-65° C.The molten system is drained into heated tanks that maintain the gelatinin a molten state during staging and casting of the films. Staging canbe as long as two to three days. Before encapsulation, other additivessuch as colorants, preservatives, sweeteners, flavors, texture modifiersand the like may be blended into the gelatin melt.

[0010] During the prior art encapsulation process, the molten gelatinmelt is transferred to the metering devices (spreader boxes) which areused to cast ribbons with a required thickness onto the casting drum.Commonly, the metering device consists of a heated reservoir that uses agate box (a heated chamber or box with the rear portion fitted with avariable height slot) wherein the material flows via gravity through theslot onto the rotating casting drum. Film thickness is determinedprimarily by the height of the slot. Item 8 in Parkhideh, U.S. Pat. No.5,761,886, is a spreader box. A second type of metering device metersthe gelatin onto the rotating casting drum using doctor blades. Arotating cylinder mounted adjacent to the doctor blade assists with theflow of the gelatin. Ribbon thickness is determined by a) the gapbetween the doctor blade and the casting drum surface; and b) the speedof the spreader box cylinder. The cast ribbon solidifies onto therotating casting drum after leaving the spreader box and this can takeup to 10 to 15 seconds to achieve. The typical spreader boxes are ventedto the atmosphere and are not capable or designed to support pressure tofacilitate the casting process.

[0011] U.S. Pat. No. 2,775,257 to Stim et al. discusses some of theshortcomings associated with the prior art gelatin film castingmachines. This reference describes the use of casting hoppers where ithas been found that the surface of the gelatin composition exposed tothe air lost moisture by evaporation and formed a comparatively hard,inflexible scum or skin. Additionally, changes in the gelatincomposition introduced by the evaporation of moisture from the surfacecaused undesirable variations in the film. Stim et al. found that byplacing a layer of an inert liquid, such as mineral oil, on the surfaceof the gelatin composition, evaporation from the hoppers was prevented.This reference also provides a fairly good description of the use of acasting hopper or spreader box to form the ribbons.

[0012] In the prior art process, transfer of molten gelatin from theholding tank to the metering device (or spreader box) is achieved in oneof two ways. A common method is to suspend or mount the tank of moltengelatin above the encapsulation machine and allow the molten material togravity feed through heated tubes into the reservoir of the meteringdevice. Another transfer method conventionally used is to pump themolten gelatin via heated tubes from floor mounted gelatin staging tanksusing either a peristaltic or lobe pump system. One shortcoming of thepump feed system is that the pump casing/components and in-lineconnections must be maintained above the melting point of thefilm-forming composition. If there are cold areas within the path, thematerial will freeze and prevent flow. In addition, both gravity andpump systems require a method of controlling flow to prevent overfillingof the spreader boxes.

[0013] The conventional process also relies on maintaining the gelatinmelt in a molten state from initial manufacture to just beforeencapsulation. Tanks used to feed the encapsulation machine require theentire tank to be maintained above the melt temperature of thefilm-forming composition. Prolonged maintenance of gelatin or otherfilm-forming compositions in a molten state leads to degradation of thepolymer, rendering the gelatin after prolonged staging, ineffective atfabricating capsules. Gelatin melts can be staged typically no longerthan 96 hours before unacceptable degradation occurs.

[0014] Gelatin can be cooled and allowed to solidify within the stagingtanks to prevent degradation if prolonged staging is required. However,the major drawback is that the entire tank contents have to be remelted.This requires 8 to 15 hours of gently heating the material to raise thetemperature of the gelatin mass to the required 60° C. Rapid heating ofthe system leads to localized heating, which can cause degradation andcharring of the composition. Therefore, when stopping the encapsulationmachine, a decision has to be made to: 1) continue to heat the gelatinwhich subjects it to degradation; or 2) allow it to solidify. Thesolidification subsequently requires the remelting which is very timeconsuming and expensive. Often, the result of stopping the encapsulationmachine is that the melt is discarded which represents a significantwaste of resources. Thermal degradation is often exacerbated by theaddition of additives and can significantly shorten the availablestaging time.

[0015] Another drawback of the conventional process and apparatus isthat it requires relatively low viscosities of the film-formingcompositions. Spreader boxes rely on viscosities sufficiently low toenable the material to flow from the exit slot. The use of doctor bladesand a rotating cylinder will enable slightly higher viscosity materialsto be cast into films, but there is still a limit of about 20,000 to25,000 cps on these metering systems. The conventional equipment andmethodology therefore precludes the use of high viscosity film-formingcompositions. Most alternative polymer compositions for forming filmshave viscosities significantly higher than that of gelatin.

[0016] An example of a film-forming composition that is not gelatinbased is disclosed in International Application No. PCT/US00/18420,entitled: FILM-FORMING COMPOSITIONS COMPRISING MODIFIED STARCHES ANDIOTA-CARRAGEENAN AND METHODS FOR MANUFACTURING SOFT CAPSULES USING SAME.In general, this application discloses an edible, soft capsule whichcomprises a soft, dry shell which comprises i) about 12-24 weight %iota-carrageenan; ii) about 30-60 weight % modified starch; iii) about10-60 weight % plasticizer; and iv) about 1-4 weight % sodium phosphatedibasic buffer system. The viscosity of these compositions can rangefrom 10,000 to above 30,000 cps and have proven to be difficult toutilize on the conventional encapsulation machinery. One aspect of thepresent invention resides in the discovery that these gelatin freecompositions can be effectively utilized in the encapsulation systemdisclosed herein.

[0017] A further limitation of conventional equipment and methodologiesis that it is extremely difficult to use a spreader box to formlaminated ribbons. Laminated ribbons are ribbons that are cast one ontop of the other. Laminated ribbons are sometimes desirable to modifythe functional properties of the film, i.e., modifying the dryingcharacteristics or retaining fill materials that are incompatible withstandard encapsulation polymers. Through the use of the inventivemelt-on-demand extrusion apparatus of the present invention, laminatedribbons are easily produced.

SUMMARY OF THE INVENTION

[0018] There is disclosed an apparatus for preparing films suitable forencapsulation from a solid film-forming material comprising:

[0019] a) at least one casting drum;

[0020] b) means for melting said film-forming material on demand;

[0021] c) pump means; and

[0022] d) an extrusion device.

[0023] The inventive encapsulation apparatus uses a conventional castingdrum known to those skilled in the art upon which to extrude the filmforming material. These drums can vary in size and may be air or liquidcooled. Typically, these casting drums are stainless steel or chromediron.

[0024] One aspect of the present process and apparatus is that thefilm-forming materials are prepared in bulk and allowed to solidify. Thematerial can be cast into blocks or bricks, or filled in 55 gallondrums. Thus, the film-forming material can be stored for long periods oftime without fear of degradation. Another aspect of the presentapparatus and process is that the solid film forming material is meltedon a continuous basis at a rate about equal to the rate ofdeposition/extrusion of the film on the casting drum. Representative“melt-on-demand” devices are disclosed below. The melted material isthen pumped under pressure to the extrusion device which has an internalcavity in the shape of a coat hanger, to facilitate the even andconsistent extrusion of the film.

[0025] The film-forming material or composition can be any materialknown in the art to be useful for encapsulation or enrobingtechnologies. Typically, these film-forming materials comprise at leastone component selected from the group consisting of starch, gelatin,carrageenans, gums or synthetic materials such ashydroxypropylatedmethylcellulose (HPMC) and the like. The film-formingmaterial typically has an aqueous base and is considered to beingestible. As used herein, the term “ingestible” is used to indicate afilm-forming material that dissolves under conditions simulating thehuman digestion tract or water.

[0026] One especially preferred film-forming material or compositionthat can be utilized in the apparatus and process of the presentapplication, is a composition comprising iota-carrageenan and at leastone modified starch selected from the group consisting ofhydroxypropylated tapioca starch, hydroxypropylated maize starch,acid-thinned hydroxypropylated corn starch, native potato starch,hydroxypropylated potato starch, pre-gelatinized modified corn starches,and wherein said starch has a hydration temperature below about 90° C.and wherein the weight ratio of modified starch to iota-carrageenanranges from 1.5:1 to about 4.0:1. This film-forming composition, whendried, consists essentially of from 42-84% by weight gel formerscomprising a mixture of iota-carrageenan and modified starch; water; aplasticizer; and a buffer. In general, any hydroxypropylated vegetablestarch would be useful in preparing the film-forming composition.

[0027] During the operation of the apparatus according to thisinvention, only that amount of film-forming material as is required ismelted in the melt-on-demand device and transported under pressure tothe casting drum. This apparatus for melting the film-forming materialcomprises a melt grid. The grid may be above the solid film-formingmaterial or below the solid film-forming material. The apparatus andprocess according to the present invention also requires the presence ofa positive displacement pump. This pump is used to transport the moltenfilm-forming material from the melter to the extrusion device. Thesepositive displacement pumps can be selected from the group consisting ofgear pumps, lobe pumps, sine pumps, worm pumps and archimedes screws.

[0028] Preferentially, the apparatus according to the inventionadditionally comprises a reservoir means disposed between said means tomelt said film forming composition and said extrusion device. Theextrusion device typically comprises a chamber and an extrusion slot.Preferably, the extrusion device is a “coat hanger” die. Even morepreferred is an encapsulation apparatus that comprises a valvedinjection wedge.

[0029] The invention also relates to an apparatus for preparing aningestible film, said apparatus comprising:

[0030] a) at least one casting drum;

[0031] b) means to melt a solid ingestible film forming composition ondemand;

[0032] c) pump means to transport the molten composition to an extrusiondevice; and

[0033] d) reservoir means disposed between said means to melt saidcomposition and said extrusion device.

[0034] The reservoir means is essentially a small tank that contains anamount of the molten composition that allows for the change out of themelt-on-demand device without stopping the encapsulation machine.

[0035] The present invention also relates to a process for thepreparation of films suitable for encapsulation comprising the steps of:

[0036] a) preparing a liquid gel mass;

[0037] b) solidifying said liquid gel mass;

[0038] c) melting only a portion of said solid gel mass as required andpumping the molten gel mass to an extrusion device; and

[0039] d) forcing the molten gel mass through said extrusion device.

[0040] There is further disclosed an apparatus for forming capsulescomprising:

[0041] a) a plurality of movable dies cooperatively forming anencapsulation region;

[0042] b) means for holding and pumping an active fill material;

[0043] c) means for holding and pumping a placebo fill material; and

[0044] d) a valve disposed between said encapsulation region and saidmeans for holding and pumping fill material, adapted to switch betweenthe placebo fill material and the active fill material.

BRIEF DESCRIPTION OF THE DRAWINGS

[0045]FIG. 1 is a front perspective view of a representative prior artmachine, partially cut away.

[0046]FIG. 2 is representative of a melt-on-demand device useful in thepresent invention, in cross section.

[0047]FIG. 3 is an extrusion device in accordance with an embodiment ofthe present invention in an exploded perspective view.

[0048]FIG. 4 is a representative melt-on-demand device in perspectiveview that is adapted for removing a solid film forming composition froma 55 gallon drum.

[0049]FIG. 5 is a perspective view of a fill material distributiondevice or injection wedge that comprises a valve for switching betweenan active fill and a placebo fill.

[0050]FIG. 5A is an exploded perspective view of an embodiment of thevalved injection wedge according to the invention.

[0051]FIG. 6 is a fill material distribution device or valved injectionwedge in cross section in the placebo fill position.

[0052]FIG. 7 is a fill material distribution device in cross-section inthe active fill position.

[0053]FIG. 8 is a process flow diagram of the ribbon casting processaccording to the present invention.

[0054] FIGS. 9-12 illustrate top (FIG. 9), side (FIG. 10) and end planviews of the back plate of one embodiment of the sanitary, low pressure,coat hanger extrusion die.

[0055]FIG. 13 is a perspective view of an assembled extrusion die usefulin the present invention.

[0056]FIG. 14 is a top plan view of the front plate of an extrusiondevice according to one embodiment of the invention.

[0057]FIG. 15 is a side plan view of the front plate of an extrusiondevice according to one embodiment of the invention.

[0058]FIG. 16 is a cross section of the front plate taken through line16-16 of FIG. 15.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0059]FIG. 1 shows a front perspective view of a typical prior art softcapsule machine 10. The motor 12 that operates the machine is shown inthe cutaway view of the base. The casting drum 9 on the right side isshown under the cutaway portion of the skin. The fill hopper 2 is shownabove the pump and pump housing 3. Element 4 is the pump lifting handle.The gelatin ribbon (not shown) starts out as liquid in spreader box 8which maintains the gelatin in a liquid state using heat. The spreaderbox 8 is typically gravity fed and places the gelatin melt on thecasting drum 9 using conventional techniques. The casting drum 9 rotatesand results in the formation of a continuous sheet or ribbon of gelatin.Cooling the molten gelatin on the casting drum creates a flexiblegelatin ribbon which is threaded through oil roller assembly 7. Anedible lubricant is typically placed on both sides of the ribbon toassist in the transfer of the ribbon to the rotary dies (not shown). Inthis machine, the ribbon makes a twist to enable it to be passed overribbon roller 5 and then to wedge 13. Two ribbons are formed in the samemanner using identical assemblies on either side of the machine (notshown). The gelatin ribbon formed on one drum provides the shellmaterial for one side of the capsule. The rotary dies are housed behindthe yoke assembly 6. The gelatin ribbons are threaded over the co-actingdies (not shown) into communication with each other. Pressure is appliedto the dies to force them against each other. This force, in conjunctionwith heat from the wedge assembly, causes the two ribbons of gelatin tobe sealed together and cut along the cavities on the dies to produce asemi-formed, empty capsule. In simultaneous action, pump assembly 3measures and dispenses the fill material (i.e., nutritionals,pharmaceuticals and the like) through the tubes 14 into the injectionwedge and then into the semi-formed, empty capsule via injection portsin the fill material distribution device or wedge. The rotation of thedies continues the sealing and cutting process to form a complete filledcapsule. Output shoots 11 receive the completed capsules. During the setup and other nonproduction phases, the fill material is returned to thefill hopper 2 via return hose 12.

[0060] In contrast, the inventive apparatus replaces the spreader box 8with a sanitary, coat hanger extrusion die. Further, the holding tankfor molten gelatin is replaced with a melt-on-demand device. Lastly, theinventive apparatus would have two fill hoppers, one for placebo filland one for action fill; two sets of fill lines 14 and two sets ofreturn lines 12. The inventive apparatus would also have a valvedinjection wedge that would allow the rapid switching from an active fillto a placebo fill and vice versa.

[0061] One embodiment of the present invention relates to the placementof a valve in the wedge injection as seen in FIGS. 5-7. Whenencapsulation machines are “set up”, they typically run withoutinjecting fill material. In the alternative, they are run using anactive fill. The placement of a valve in the wedge provides theadvantage that the machine can be set up with placebo and then quicklyswitched over to the active fill material. This has the advantage ofbeing able to make soft capsules with very small amounts of raw materialand conserve the active fill. In this embodiment, a second hopper andpump is utilized and filled with placebo fill material.

[0062]FIG. 2 is illustrative of one version of a melt-on-demand deviceuseful in the present invention. The device 20 generally consists ofinsulated walls 21 and a melt grid 38. The solid film-formingcomposition is represented by blocks 22 inside the device 20. Access tothe interior of the device 20 is through door 23. The solid film-formingmaterial 22 rests upon the melt grid 38. This melt grid 38 is slopedslightly and provides an area of molten film-forming material 30 betweenthe solid 22 and the melt grid 38. This molten material 30 entersthrough gateway 32 into gear pump 24. Gear pump 24 provides thenecessary pressure for line 34 which is connected to a heated hose 36that proceeds to the extrusion die. A pressure feedback line 28 and apressure relief valve 26 are disposed within manifold block 40. Thepressure relief valve 26 controls the amount of molten material 30flowing through heated hose 36 to the extrusion die (not shown) or beingrecycled back through the melt grid 38 to the pool of molten material 30between the solid film forming material 22 and the melt grid 38.

[0063] The gear pump 24 can be carefully controlled in conjunction withthe pressure relief valve 26 to provide a steady and consistent supplyof molten film-forming material to the extrusion die. In one embodiment,a reservoir is disposed between the pump of the melt-on-demand device 20and the extrusion device (not shown).

[0064] Referring now to FIG. 3, shown is one embodiment of the extrusiondevice in exploded perspective. The main body 50 contains the coathanger type cavity 68 and lip 72. Entrance port 52 is where the moltenfilm-forming material enters the extrusion device under pressure ofabout 10-35 psi (about 70 to 245 kPa). The front face of the main body67 is in contact with a shim 66. The shim contains a cut out 69 andnumerous holes 64 to accommodate bolts 60. The shim cut out 69 can beadjusted to alter the thickness of the ribbon. In an alternativeembodiment, the shim may be eliminated and the front plate 62 may havean opening or cut out placed therein. Bolts 60 pass through the frontplate 62, the shim and into the main body 50 of the extrusion device. Ona side adjacent the front face 67 of the main body 50 are heatingelements 58, end piece 56 and port 70 for electrical connections. Agasket 54 is disposed between the main body 50 and the end piece 56.

[0065] The heating elements 58 contained within the main body arecarefully controlled by thermisters (not shown). The temperature of thefilm-forming material at the point of exit from the extrusion device iscritical to extruding a high quality film. The inventors have alsodetermined that the pressure at the lip 72 is critical in obtaining anacceptable ribbon. In addition, the height of the lip is important. Thelip should be of a height of from ½ to 1 inches (about 1 to 2.5 cm).

[0066] Further, the pressure differential across the face of the openingof the extrusion device should vary by no more than 2%. In general, thepressure of the film-forming composition in the extrusion device isabout 10-12 psi (about 70 to about 85 kPa) at the entrance port 52. Thecoat hanger design can be varied depending upon the viscosity andtemperature of the film-forming composition. What is important indesigning the extrusion device is that laminar flow and laminarthickness occur across the entire opening or shim cut out 69 and downthe lip 72 of the extrusion device. Through the application of evenpressure at a given temperature, and the design of the coat hangercavity 68, a wide variety of film-forming materials can be cast upon thecasting drum to result in an acceptable encapsulation film.

[0067]FIG. 4 is an alternative melt-on-demand device that is morespecifically known as a drum unloader 80. This particular device has thesolid film-forming material in a 55 gallon drum 96. This drum sits upona base 94. The melt-on-demand device 80 further comprises a motor 82, agear box 86 connected to a shaft 90 which is then connected to a pump100 and a distribution manifold 102. A tie bar 84 communicates withpneumatic cylinders 92 and tie rods 88 to have the entire unit move upand down in a vertical fashion. The platen or melt grid 98 is heated andmelts the solid film-forming material in the drum 96 which is forcedinto the pump 10 cavity and out through the distribution manifold 102.Representative of such a melt-on-demand device are the Dynadrum™ 55manufactured by ITW Dynatec of Hendersonville, Tenn.; Uniflow Productmanufactured by Industrial Machine Manufacturing, Inc. of Richmond, Va.;and Robotech AG of Switzerland.

[0068] This melt on demand device was originally developed for theapplication of hot melt adhesive glues to packaging and the like.Substantial modifications of these machines have been made toaccommodate film-forming compositions which are useful in the productionof soft capsules using the rotary die process. Modifications includeprotecting parts that contact the film-forming material to preventcorrosion and modifications to the melting platen 98 to obtain the flowrequired to the extrusion die. The platen or melt grid 98 are typicallyfabricated from aluminum, anodized and coated withpolytetrafluoroethylene (Teflon®). The Teflon surface is used to reducethe frictional forces of solid, film-forming material moving towards themelt grid 98. This melt-on-demand device utilizes pneumatic rams 92 topush the heated platen 98 into a 55 gallon drum where the solidfilm-forming material is melted and removed by the gear pump 100. Thedistribution manifold 102 may have one or more hose units connected toit. These electrically heated hoses (not shown) preferably have onepiece stainless steel hose fittings which eliminates cavities and thusprevents contamination. These heated hoses must be constructed so thatthey may be cleaned of the highly viscous film-forming material. Suchhoses are available from Viking Industries, Inc. of New Smyrna Beach,Fla.

[0069] One important benefit of the melt-on-demand devices representedin FIGS. 2 and 4 is that they prevent charring of the film-formingmaterial. As heat is applied to a film-forming material, the complexpolymers break down and degrade and continue to do so as temperature andtime increase. The prior art methodology and apparatus for maintainingthe film-forming materials in a molten condition results in charringsince oxygen is typically present. The present inventors have determinedthat by carefully controlling the heat applied to the solid film-formingmaterial in the melt-on-demand devices, that charring can be greatlyreduced and virtually eliminated through the exclusion of oxygen in thesystem.

[0070] The use of such melt-on-demand devices in the encapsulationindustry is unique and provides tremendous advantages over the prior artmethods and apparatuses. The system according to the present inventionprovides temperature stability in each melt zone, reduction of heattransfer from one zone to another, isolation of film-forming materialsat high temperatures from oxygen, in a sanitary, easily cleanabledevice.

[0071]FIG. 5 is a perspective view and represents another aspect of thepresent invention that relates to a valved injection wedge, generally110. The wedge in an encapsulation machine is the device that insertsthe fill material in between the two films just prior to the nip of thetwo rotary dies completing the capsule. Injection wedges are typicallyheated to pretreat the films prior to capsule formation and contain anumber of fill exit ports 111 at or next to the apex of the wedge. Thenumber of exit ports 111 will equal the number of rows of cavities inthe rotary dies. The valved wedge 110 replaces the conventional wedgeand shut-off valve as seen in U.S. Pat. No. 5,761,886 at elements 27 and13 and item 26 in U.S. 6,022,499. The wedge according to the presentinvention differs from those of the prior art in that it allows theprompt switching from a placebo fill material to an active fill materialand vice versa. This allows the machine to be set-up without wastingvaluable active fill material. Typically during the set-up ofencapsulation machines only some of the machine settings can be madewithout using fill material. Complete machine set-up requires the use offill material. The valved wedge according to the invention requiresseparate pumping and reservoir capability for the placebo and activefill materials.

[0072] Thus, in operation, the encapsulation machine operator can beginthe set-up of the machine through the use of a placebo fill. This wouldbe accomplished by having lever 112 in the placebo position. See FIG. 6.After accomplishing the proper set up of the encapsulation machine, theoperator would move the lever 112 to the active position as seen in FIG.7. An encapsulation apparatus with a valved injection wedge isespecially useful for the manufacture of small quantities of softcapsules. This ability to switch from placebo to active fill is anadvancement in the state of the art in terms of the amount of activematerial required to manufacture the soft capsules and the quality ofthe final product.

[0073] In essence, the valved injection wedge is a three-way valve foreach injection port 111. While three way valves are well known, thenovel aspect of this invention is its application to rotary dieencapsulation processes.

[0074]FIG. 5A represents an exploded perspective view of the valvedinjection wedge illustrated in FIG. 5. Those skilled in the art willappreciate that the valved injection wedge set forth in FIGS. 5, 5A, 6and 7 would produce only one row of capsules as there is only one fillexit port 111. Commercial scale valved injection wedges would containernumerous fill exit ports, i.e., 5 to 15.

[0075] Referring to FIGS. 5, 5A, 6 and 7, elements 113-116 arepreferably quick star push-in fittings. Fitting 113 is the active returnport; 114 is the active injector port; 115 is the placebo return port;and 116 is the placebo injector port. The valve is designed so that ifactive fill is selected, the placebo fill recirculates from the injectorport 116, out the placebo return port 115 and back to the placebo fillreservoir (not shown). In similar fashion, when placebo is selected,active fill material recirculates. When neither active nor placebo areselected (the off position), both placebo and actives recirculate. Wedgeapex 118 is positioned very near the nip of the dies. Elements 119 areopenings for placement of heating elements.

[0076] In FIG. 6, the flow channel 120 of placebo fill is placed intochannel 124 that exits near the apex 118 of the wedge through exit ports111. The active flow line 122 is opened by moving the lever to the downposition so that active injector 114 aligns with line 122, that alignswith line 124, which in turn aligns with exit ports 111. Element 111 isthe exit port on each side of the wedge. For purposes of illustration,only one set of exit ports are shown. In commercial production, thenumber of pairs of exit ports 111 will equal the number of cavitiesacross a face of the rotary die.

[0077]FIG. 8 is a block diagram of the method according to the presentinvention wherein each block represents an apparatus component. Theessence of the present invention resides in the use of a melt-on-demanddevice in combination with a pump to supply an extrusion device thatutilizes laminar flow technology to cast a high quality ribbon upon thecasting drum. The ribbons produced using the apparatus and processdescribed herein are very uniform in thickness with very few defects.

[0078] The present invention differs from the prior art in the aspectsof staging the film-forming composition and the method of producing theribbon on the casting drum. The film-forming composition may be producedin a manner described in the prior art or using new compositions. In thepresent invention, the liquid, film-forming composition is placed withina container (i.e., a 55 gallon drum) or a reservoir of a melt-on-demanddevice and allowed to solidify.

[0079] Further, the present invention is different from the prior art inthat the spreader box is replaced with an extrusion die (See FIG. 13).The die is different from a spreader box in that the film-formingcomposition is pumped under pressure through a slot under laminar flow.The uniform thickness of the ribbon is also achieved through a design ofthe extrusion die that provides for equal pressure distribution acrossthe die opening. Further, the extrusion die is so designed internallythat the rate of flow is substantially even across the exit slot (lip)of the die. This is achieved by means of a carefully designed “coathanger” cavity that feeds the extrusion lip with material (See FIGS. 10and 11). This cavity, somewhat in the shape of a “coat hanger” is anintegral part of the extrusion die. The body of the extrusion die isheated to a few degrees Celsius (i.e., 2-10° C.), above the meltingpoint of the film-forming composition. Unlike a spreader box, there isno reservoir of material and the ribbons are extruded under pressure.

[0080] Due to the ability of extrusion dies to produce films usingpressurized film-forming material, the corresponding viscosities of thefilm-forming polymers may be significantly higher than the viscositylimits imposed by the prior art spreader box technology. Examples offilms formed with viscosities at the casting temperature in the regionof 80,000 to 120,000 cps have been produced.

[0081]FIG. 13 is a perspective view of a slightly different extrusiondie from that shown in FIG. 3. The die according to FIG. 13, generally130, comprises a film forming material entrance port 132, a back plate134, and a front plate 136. The front plate 136 and the back plate 134are attached to each other by numerous bolts 138. The ribbon to beextruded from the die is depicted as element 140. The extrusion slot 142is an opening between the back plate 134 and the front plate 136.

[0082]FIG. 9 is a top plan view of the back plate 134 of the extrusiondie. Connecting bolt holes 144 are for attachment of the die to theencapsulation machine, while bolt holes 146 are for attachment of thefront plate 136 to the back plate 134. FIG. 10 is a side view of theback plate showing the “coat-hanger” cavity 146 of the die.

[0083]FIG. 11 is a cross section taken through FIG. 10 at line 11-11showing the coat-hanger cavity 146 and cavities 150 for heating elements(not shown). FIG. 12 is a cross section taken through FIG. 10 at line12-12 showing cavities 150 for the heating elements and thermisters 152that are used to control the heating elements 150.

[0084]FIG. 14 is a top plan view of the front plate 136 illustrating thefilm-forming material entrance port 132 and numerous bolt holes 154.FIG. 15 is a side plan view of the front plate 136 of the extrusiondevice 130 illustrating the film forming material entrance port 132 andnumerous bolt holes 154.

[0085]FIG. 16 is a cross section of FIG. 15 taken through line 16-16illustrating the film forming material entrance port 132.

[0086] Because the inventive system is an enclosed system, there areother advantages over the prior art spreader boxes. The open reservoirsof the spreader box are prone to water loss from the film-formingcomposition due to evaporation. In addition, the reservoir requires theadditional complexity of a level feedback mechanism to control thefilling of the spreader box chamber and prevent overflow. The extrusiondies of the present invention are in closed systems and can operate athigher temperatures if desired, without concerns for water loss. Theinventive controlled and enclosed system exhibits better thermal controlof the film-forming material being extruded. Further, extrusion diesovercome the inherent inaccuracies of spreader boxes which rarelyproduce geometrically even ribbons. It has been found that the extrusiondies according to the invention reduces the factors that causevariations in film thicknesses. It has been found that using theapparatus and process according to this invention, that the filmsproduced are dimensionally more accurate and have considerably lessdimensional variability than films produced using the prior art spreaderboxes.

[0087] In addition, extrusion dies can be fabricated with a plurality ofexit slots each individually fed with a different type of film-formingmaterial. The slots can be mounted in series within a close proximity,i.e., within the same die body. Alternatively, the extrusion die can beso designed to accept a multitude of different feeds exiting into aninternal die cavity/extrusion slot. In this way, the production ofmultilaminated ribbons can be enabled. Each laminate may have a separatecomposition and again, this offers further differentiation andversatility over the old spreader box technology.

[0088] A preferred type of pump for use in the inventive apparatus is agear pump, however, other types of small lobe, helical worm, or pistonpumps may suffice. The melt-on-demand devices should maintain the pumpsat about the same temperature as the melt grid. The pump forces the flowof the film-forming material through heated tubes to the extrusion die.The speed of the pump determines the amount of material delivered to theextrusion die and hence, determines the thickness of the film extrudedonto the casting drum.

INDUSTRIAL APPLICABILITY

[0089] The present inventive apparatus and process allows for the use ofhigh viscosity film-forming systems for fabricating soft capsules. Onelimitation of the spreader box system of the prior art is the inabilityto produce ribbons or films from compositions that have viscosities inexcess of 10,000 to 15,000 cps. Extrusion dies on the other hand, havebeen shown to easily handle 80 to 200,000 cps film-forming compositions.

[0090] One advantage of the inventive apparatus and process is theutilization of melt-on-demand technology as it overcomes the undesirablethermal degradation of the film-forming compositions. Gelatin is atypical polymer system used to manufacture soft capsules, however, usingthe current spreader box process requires the material to remain moltenthroughout use. Gelatin can only be kept in its molten state for 96hours before sufficient degradation has occurred to render the systemineffective for making soft capsules. In contrast, the apparatus andprocess according to this invention heats the film-forming material onlyfor 15 to 30 minutes prior to use. This is insufficient for undesirabledegradation and loss of polymer function to occur. The apparatus andprocess according to the present invention provide a significant advancein the state of the art.

[0091] In the foregoing, there is provided a detailed description ofpreferred embodiments of the present invention for the purpose ofillustration and not limitation. It is to be understood that all othermodifications, ramifications and equivalents obvious to those havingskill in the art based on this disclosure are intended to be within thescope of the invention as claimed.

We claim:
 1. An apparatus for encapsulation comprising: a) at least onecasting drum; and b) a valved injection wedge.
 2. The apparatusaccording to claim 1 wherein said valved injection wedge comprisesinjection ports and return ports.
 3. The apparatus according to claim 2additionally comprising at least two fill hoppers and at least two setsof fill lines and at least two sets of return lines.
 4. The apparatusaccording to claim 3 wherein said valved injection wedge comprises fillexit ports and a distributor/shut-off plate.
 5. The apparatus accordingto claim 1 wherein said valved injection wedge comprises heatingelements.
 6. The apparatus according to claim 1 wherein said valvedinjection wedge has at least three valve positions.
 7. The apparatusaccording to claim 6 wherein said three valve positions are closed,active fill and placebo fill.
 8. The apparatus according to claim 1additionally comprising at least two pumps.
 9. The apparatus accordingto claim 8 wherein said pumps are active fill pumps and placebo fillpumps.
 10. The apparatus according to claim 1 wherein said valvedinjection wedge is a three-way valve.
 11. The apparatus according toclaim 1 wherein said valved injection wedge is adapted to switch fromplacebo fill to active fill and vice versa.
 12. The apparatus accordingto claim 1 wherein said valved injection wedge comprises a three wayvalve.
 13. The apparatus according to claim 1 additionally comprising anextrusion device.
 14. An apparatus for applying a polymer to a substratecomprising: a) means to melt said polymer on demand; and b) a three-wayvalved injection wedge.
 15. The apparatus according to claim 13 whereinsaid extrusion device comprises a chamber and an extrusion slot.
 16. Theapparatus according to claim 15 wherein said extrusion device is a coathanger die.
 17. The apparatus according to claim 14 additionallycomprising at least two fill hoppers, at least two sets of fill linesand at least two sets of return lines.
 18. An apparatus for formingcapsules comprising: a) a plurality of movable dies cooperativelyforming an encapsulation region; b) means for holding and pumping anactive fill material; c) means for holding and pumping a placebo fillmaterial; and d) a valve disposed between said encapsulation region andsaid means for holding and pumping fill material, adapted to switch fromplacebo fill material and active fill material.
 19. The apparatusaccording to claim 18 additionally comprising active return means andplacebo return means.